Running head: INDIVIDUAL DIFFERENCES IN MATERNAL SOOTHING EFFECTS
Individual Differences in the Effectiveness of Maternal Soothing on Reducing Infant Distress
Response
Laudan B. Jahromi
University of California, Los Angeles
Cynthia A. Stifter
The Pennsylvania State University
Please address correspondence to:
Laudan B. Jahromi
UCLA Graduate School of Education and Information Studies
Box 951521, 3132B Moore Hall
Los Angeles, CA 90095-1521
Phone: (310) 351-3578
Fax: (949) 387-8867
Email: jahromi@ucla.edu
Individual Differences 1
Running head: INDIVIDUAL DIFFERENCES IN MATERNAL SOOTHING EFFECTS
Individual Differences in the Effectiveness of Maternal Soothing on Reducing Infant Distress
Response
Individual Differences 2
SYNOPSIS
Objective. The present study investigates individual differences in the effectiveness of specific
maternal regulatory behaviors on reducing the intensity and duration of infants’ distress to an
inoculation. Additionally, we examined the stability of infants’ stress responses and the stability
of specific maternal soothing behaviors. Design. The sample included 128 mother-infant dyads
that were observed during an inoculation at 2- and 6-months. The intensity and duration of
infants’ distress responses and eight specific maternal soothing behaviors were subsequently
coded. Results. The intensity of infant cry response was stable across age, but the duration of
crying was not. Of the eight specific maternal regulatory behaviors studied, affection, touching,
vocalizing, caretaking, and feeding/pacifying were stable across infant age. Finally, an index of
the overall effectiveness of maternal soothing behaviors at 2 months negatively predicted cry
duration but not cry intensity at 6 months. Conclusions. The results of the present study found
that infants of mothers who were effective at soothing their distress at 2 months showed a shorter
duration of crying 4 months later, suggesting the possible influence of maternal regulation on
infants’ development of self-regulation over time.
Individual Differences 3
Individual Differences in the Effectiveness of Maternal Soothing on Reducing Infant Distress
Response
Infants display varied responses to negative stimuli, even those as aversive as pain.
Differences exist in a number of infants’ response dimensions, including the intensity of reaction
to stimuli as well as the duration of recovery from distress. These dimensions reflect the
reactivity and regulation components of infant temperament (Rothbart & Derryberry, 1981;
Thompson, 1994). While there exist a variety of approaches to the study of temperament, many
in the field agree that temperament has a constitutional basis, is relatively stable, and with the
influence of the infants’ caregiving environments, may have a profound effect on infants’ social
and emotional development (e.g., Buss, 1991; Chess and Thomas, 1973; Goldsmith & Campos,
1982; Rothbart and Derryberry, 1981). A number of studies have explored individual
differences in infants’ responses to negative stimuli (e.g., Braungart & Stifter, 1996; Fish, Stifter,
& Belsky, 1991; Riese, 1987), but there exist few person-centered approaches to infants’
responses to pain. Moreover, the individual variability and influence of maternal soothing
behaviors in these situations has received little attention. Understanding the systematic variation
of infants’ and mothers’ behaviors, and the soothing effect of specific maternal behaviors in the
context of pain is significant because unrelieved distress in early infancy may have serious long
term influences on infants’ wellbeing (Anand & McGrath, 1993; Craig, Gilbert-MacLeod, &
Lilley, 2000; Porter, Grunau, & Anand, 1999). To this end, the present study examined the
stability of infants’ reactions to an inoculation, the stability of mothers’ use of specific soothing
behaviors in this context, and the influence of effective maternal soothing on infants’ responses
across time.
Individual Differences 4
Many agree that the soothing environment provided by the mother serves not only the
purpose of alleviating immediate distress, but is also important for facilitating the infant’s
development of self-regulation (Kopp, 1989; Thompson, 1994). Soothing a distressed infant
affords caregivers the opportunity to model emotion regulatory strategies and to demonstrate the
effectiveness of various behaviors for reducing distress. Thus, theoretically, infants whose
mothers engage in more appropriate and effective regulatory strategies may become better selfregulators than infants who experience less effective early external regulation. Investigating the
effect of early maternal soothing on later infant reactivity, therefore, may be important toward
furthering our understanding of the development of self-regulation.
Currently there exists no longitudinal work on whether early effective maternal soothing
predicts infants’ level of negative reactivity. There is, however, some evidence of this
hypothesized process from research concerning other aspects of the caregiving environment,
including maternal sensitivity and responsiveness. Maternal sensitivity and responsiveness are
characterized by behaviors which include recognition of infant signals, as well as prompt,
contingent, and appropriate responses to those signals (Ainsworth, Bell, & Stayton, 1971;
Bornstein & Tamis-LeMonda, 1989). Studies have found that the mothers of infants who
remained low in negative reactivity from birth to 5 months were more sensitive than those of
infants who increased in crying over time (Fish, Stifter, & Belsky,1991), and that parents of
infants who changed from higher to lower levels of negative reactivity between 3 to 9 months
engaged in more sensitive and complimentary interactions with their infants than the parents
whose infants increased in level of negative reactivity (Belsky, Fish, & Isabella, 1991).
Additionally, early maternal responsiveness was associated with less frequent and shorter
durations of spontaneous infant crying across the first year (Bell & Ainsworth, 1972), and an
Individual Differences 5
intervention designed to increase maternal responsiveness in mothers of irritable newborns
resulted in these babies becoming more sociable and self-soothing, and less petulant across age
(van den Boom, 1994). These studies have implications for other developmental processes. For
example, Cassidy (1994) proposed that children with limited or heightened negative emotionality
may be more likely to develop insecure attachments.
There are, however, some contradictory findings concerning outcomes associated with
maternal sensitivity and responsiveness and infant negative reactivity. Specifically, St. JamesRoberts, Conroy, and Wilsher (1998) found that while below-optimum maternal sensitivity was
associated with a moderate increase in crying overall, persistent infant crying occurred in spite of
sensitive caregiving. Additionally, Spinrad and Stifter (2002) found that responsive mothers at 5
months were more likely to have infants who were categorized as “angry-distressed” at 10
months. These inconsistent, and in some cases counterintuitive, findings may highlight the
importance of using narrower operational definitions of maternal sensitivity and responsiveness.
Thompson (1997) and Goldberg, Grusec, and Jenkins (1999) argue for researchers to consider
multifaceted aspects of the parent-infant relationship and how the infant’s changing needs may
influence the quality of sensitivity when defining these parental behaviors. For example,
maternal sensitivity at times when the infant is highly distressed may be a better predictor of later
outcomes (e.g., secure attachment) than that which occurs in nonstressful contexts. Furthermore,
quick and appropriate responses may be more indicative of sensitivity for young infants whereas
scaffolding behaviors may be more important by the end of the first year (Thompson, 1997). In
Spinrad and Stifter’s (2002) study, for example, maternal responsiveness was measured during
free play sessions, a context less likely to elicit negative responses. Assessing maternal
responsiveness within the context of distress may have yielded different findings. Indeed,
Individual Differences 6
Goldberg et al. (1999) suggest that studies which address characteristics of parenting behavior
having to do with protection, such as physical discomfort or painful procedures, may show the
strongest predictive relations to later infant behavior. By examining infants’ and mothers’
behaviors in a situation involving extreme distress, therefore, the present study may be wellsuited to predict infant reactivity and regulation across age.
To best understand the longitudinal effect of maternal soothing on infant reactivity, it is
important to also identify and describe individual variability in mothers’ and infants’ behaviors
across time. Research concerning developmental changes in maternal soothing and infant
reactivity in the context of an inoculation is a first step toward this end. While findings
concerning overall maternal soothing from 2 to 6 months suggest a decline in maternal soothing
over infant age (Lewis & Ramsay, 1999), studies of specific maternal behaviors reveal that from
2 to 24 months, mothers use vocal soothing more frequently for younger infants and vocal
distraction more frequently for older infants (Craig, McMahon, Morison, & Zaskow, 1984).
Moreover, in a detailed analysis of maternal behaviors following an inoculation, Jahromi,
Putnam, and Stifter (in press) found that mothers’ affection and touching behaviors decreased
across age while vocalization and distraction increased. Thus, the developmental findings
suggest some discontinuity in maternal soothing such that mothers may change their use of
certain behaviors to reflect infants’ developmental maturation.
Individual variability in maternal soothing across age has received little empirical
attention. In the context of an inoculation, Lewis and Ramsay (1999) found that overall maternal
soothing was stable between 2 and 4, and 4 and 6 months. That is, mothers maintained their
relative rank in the overall use of soothing behavior across time. Furthermore, maternal soothing
in the inoculation setting was found to be related to soothing behavior to everyday distress such
Individual Differences 7
as a diaper changing or feeding. These findings suggest that infants may experience some
consistency in external soothing in the first year.
While research on individual variability in discrete maternal soothing behaviors is
limited, we return to considering research concerning other aspects of the caregiving
environment, including maternal sensitivity and responsiveness, to gain some insight on this
subject. In one study, maternal sensitivity was found to be a stable characteristic when measured
in a neonatal care unit and again during face-to-face interaction at 3 months (Meier, Wolke,
Gutbrod, & Rust, 2003). Studies have also revealed cross-age stability in maternal
responsiveness to crying (Bell & Ainsworth, 1972; Fish & Crockenberg, 1981; Stifter &
Braungart, 1992) and in other less distressing contexts such as free play (Masur & Turner, 2001;
Nicely, Tamis-LeMonda, & Grolnick, 1999; Spinrad & Stifter, 2002). Interestingly, however,
Bornstein and Tamis-Lemonda (1990) found no stability in maternal responsiveness to either
spontaneous distress or non-distress vocalizations of 2 to 5 month old infants, and Crockenberg
and McClusky (1986) found no relation between maternal responsiveness at 3 months and
maternal sensitivity at 12 months. Thus, the evidence is mixed on the stability of caregiving
style across infancy. These varied findings may be due to differences in how and where
maternal responsiveness was assessed. No study to date, however, has examined the stability of
maternal responsiveness, or that of specific maternal behaviors, within the context of infant pain
reactivity. We anticipate that, given the potency of inoculation as an elicitor of infant negative
reactivity, such a context may elicit a consistent set of specific maternal behaviors intended to
regulate infant distress.
With respect to infant negative reactivity, research on developmental changes in infants’
reactions to painful stimuli suggests that both the intensity and duration of responses tend to
Individual Differences 8
decrease across age (Craig, McMahon, Morison, & Zaskow, 1984; Jahromi, Putnam, & Stifter, in
press; Ramsay & Lewis, 1994). Studies of the individual stability of infant stress response have
demonstrated significant consistency in some response dimensions across early infancy. For
example, Worobey and Lewis (1989) found a relation between infants’ reaction to a heelstick at
2 days and an inoculation at 2 months. Specifically, this study found both the intensity of initial
reaction and average intensity of reaction to be significantly related across time, with the
strongest stability for the initial reaction to the stimulus. However, no stability was found for the
duration of reaction across age. Similarly, Lewis and Ramsay (1995) found cross-age stability in
infants’ initial reaction to an inoculation at 2 and 6 months, but no stability in the duration of
maximum response or quieting. Further evidence of stability in infants’ behavioral responses to
inoculation comes from studies which measure infants’ facial emotional expressions in this
context. Specifically, the expressions of pain and distress following an inoculation have been
shown to be stable between 3 and 5, and 5 and 11 months of age (Axia & Bonichini, 1998), and
the type and duration of anger and sadness facial expressions were stable between 7 and 19
months of age (Izard, Hembree, & Huebner, 1987). Finally, there is evidence of an association
between preschoolers’ level of distress to immunization (e.g., resistance, muscular rigidity,
crying, and screaming) and the child’s likelihood to be rated as having a “difficult” temperament
(Schechter, et al., 1991). This finding suggests that children’s pain responses may be consistent
with negative reactivity in other contexts and reflective of the child’s temperament. However,
while there is some consensus regarding the stability of infants’ post-inoculation responses,
findings of instability also exist. Specifically, Gunnar, Brodersen, Krueger, and Rigatuso (1996)
reported no stability in behavioral distress to inoculation between 2 to 15 months, but stability in
time to calm between 6 and 15 months. The mixed findings of stability in infant reactivity and
Individual Differences 9
regulation across time may be due to the emergence of self-regulation during the first year of the
infant’s life. According to Kopp (1982), by 3 months of age infants may engage in sensorimotor
modulation and become able to change ongoing behavior in response to events and stimuli in the
environment around them. During this time, infants display the ability to stimulate or soothe
themselves (Rothbart, Ziaie, and O’Boyle, 1992). By about 6.5 months of age, infants become
more active stimulus seekers, show greater use of organized motor behaviors, and are better able
to redirect their visual attention (Rothbart, Ziaie, and O’Boyle, 1992). This burgeoning ability to
self-regulate, therefore, may explain the findings that duration of crying may be unstable early in
the first year (e.g., Lewis & Ramsay, 1995; Worobey & Lewis, 1989), but stable toward the end
of the first year (e.g. Gunnar et al., 1996).
The present study extends previous longitudinal research on maternal regulation of infant
pain reactivity to an inoculation. The inoculation setting provides an ideal context in which to
study infants’ and mothers’ behaviors. This naturalistic situation is a strong elicitor of infant
stress responses and also allows for the observation of a range of maternal soothing strategies.
Our first goal was to examine individual differences in infants’ stress response to an inoculation.
Previous work suggests that the intensity and duration of infants’ responses to stress may be
independent and individually meaningful (Barr & Gunnar, 2000; Worobey & Lewis, 1989). As
such, we assessed relations between infants’ overall cry intensity and overall cry duration,
concurrently and across age. Our second goal was to examine individual differences in specific
maternal soothing behaviors. Driven by previous work concerning specific maternal soothing
behaviors utilized in the inoculation setting (Jahromi, Putnam, & Stifter, in press), we assessed
the stability of mothers’ affection, touching, holding/rocking, vocalizing, caretaking, distraction,
presenting face, and feeding/pacifying behaviors. Our final goal was to examine whether early
Individual Differences 10
effective maternal soothing predicted infant stress response across age. We expected that infants
of mothers who were effective at regulating their distress at 2 months would show more
regulated stress responses at 6 months.
METHODS
Participants
As part of a longitudinal study of healthy, term infants, 128 participants (65 female, 63
male) were observed with their mothers during an inoculation when the infants were 2 and 6
months old. At the 2-month observation, infants had a mean age of 2.1 months (range = 1.5 to
3.5 months), and at the 6-month observation, a mean age of 6.4 months (range = 5.0 to 8.8
months). Families were predominantly Caucasian (4 African American, 4 Asian, and 1
Hispanic), and were recruited from a local community hospital. Eighty-four percent of the
mothers were married, and 96% were living with the infant’s father. At the time of recruitment,
mothers had a mean age of 29.7 years (range =16 to 43 years) and an average of 15.7 years of
education (range = 10 to 26 years).
Procedures
Infants and their mothers were observed during a routine inoculation visit at a total of
fifteen different pediatric offices. The infant’s state of general irritability was assessed while the
infant and mother were in the waiting area and up to one minute prior to the inoculation. The
inoculation consisted of between one to four injections. After receiving the shot, the infant was
given to the mother, who was free to soothe her infant using any method she deemed appropriate.
Although consistent procedures were used across doctor’s offices, the doctor’s office and the
number of injections were noted by the experimenter and examined with respect to the outcome
variables.
Individual Differences 11
Measures
Infants and their mothers were videotaped for at least one minute prior to the
administration of the shot, and until the subject was calm for a period of 20 consecutive seconds
following the inoculation. The videotapes were subsequently coded independently for infant and
maternal variables. Coding of infant reactivity and maternal soothing behaviors began once the
last needle was retracted, and continued for a period of up to 4 minutes after the start of the
inoculation. Infant reactivity and maternal behaviors were coded in 5-second intervals, for a
maximum of 48 intervals.
Infant Variables. The infant’s state of general irritability prior to the inoculation was
measured according to a 9-point Likert-type scale adapted from the Irritability item of the
Brazelton Neonatal Behavioral Assessment Scale (Brazelton, 1973). The scale ranged from no
irritability (1), to irritable to all degrees of stimulation (9).
Infant negative reactivity was coded every 5 seconds according to the following 4-point
scale, representing an increasing intensity of negative affect: 0 (no audible vocalization), 1
(fussing, whining, or whimpering, but not crying), 2 (low intensity crying which may have
occurred at a rapid frequency, but without shrieking cries), 3 (very intense, loud, piercing,
crying, usually with a quavering out-of-control quality, and typically with a red face, squinted
eyes, and an open mouth). If more than one level of intensity of crying was observed during a 5second interval, the predominant intensity level during that interval was coded. Scores were
averaged across the number of intervals observed to produce the measure of overall cry intensity.
The measure of overall cry duration reflected the total number of intervals during which the
infant was coded as distressed.
Individual Differences 12
Ten percent of all infant reactivity observations were coded by two independent coders.
Training occurred until coders achieved a Cohen’s kappa > .75. The mean inter-rater reliability
across the 2- and 6-month observations of infant reactivity was Cohen’s kappa = .92.
Maternal Variables. The presence or absence of the following eight maternal soothing
behaviors was coded in 5-second intervals: affection (e.g., kissing or hugging), touching (e.g.,
patting or stroking), holding/rocking (i.e., picking up the infant with or without any movement),
vocalizing (e.g., talking, singing, “shushing” or making unrecognizable noises), caretaking (e.g.,
dressing, changing a diaper or wiping the infant’s nose), distracting (i.e., overtly attempting to
direct infant’s attention away from discomfort of the shot), presenting face (i.e., overtly
attempting to look into infant’s face), and feeding/pacifying (i.e., giving the infant a bottle or
pacifier, or breastfeeding). An unlimited number of maternal variables could be coded as present
during each interval, as the behaviors were not mutually exclusive. The variables represent the
proportion of time that the mother engaged in the given behavior (i.e., the total number of
intervals that the specific maternal behavior was present, divided by the total number of intervals
during which the infant cried). Ten percent of all maternal behavior observations were coded by
two independent coders after an acceptable agreement (Cohen’s kappa > .75) was achieved in
training. Coders achieved the following Cohen’s kappa for each of the soothing behaviors: .83
(affection), .78 (touching), .93 (holding/rocking), .85 (vocalizing), .89 (caretaking), .80
(distracting), .90 (presenting face), and .98 (feeding/pacifying).
RESULTS
Results are presented in the following order: (1) tests of the stability of individual
differences in infant stress responses; (2) tests of concurrent and predictive relations between
infant response dimensions; (3) test of the stability of individual differences in specific maternal
Individual Differences 13
soothing behaviors; (4) correlational analyses of maternal behaviors and infant stress responses;
and (5) tests of the cross-age relation between effective maternal soothing and infant stress
response.
Prior to conducting these analyses, we examined whether differences existed in infant cry
variables or maternal behavior variables as a function of infant sex using one-way analyses of
variance (ANOVAs). These tests revealed that infants’ and mothers’ behaviors did not
significantly differ between boys and girls. Thus, all subsequent analyses were conducted with
the combined sample.
Additionally, we tested the relations among possible covariates (i.e., general irritability,
number of shots, and doctor’s office) and infant cry variables. The mean general irritability
scores were 5.81 (SD = 1.47) at 2 months and 5.34 (SD = 1.57) at 6 months. At 2 months,
infants’ general irritability was related to concurrent measures of overall cry intensity, rs (127) =
.34, p<.001, and overall cry duration, rs (127) = .30, p<.01. At 6 months, infants’ general
irritability was also related to concurrent measures of overall cry intensity, rs (125) = .60, p<.001,
and overall cry duration, rs (125) = .46, p<.001. Thus, we controlled for general irritability in all
analyses involving these cry variables.
Infants received an average of 2.6 (SD = .87) shots at the 2 month visit, and 2.4 shots (SD
= .65) at 6 months. The number of shots at 6 months was related to concurrent measures of
overall cry intensity, r (127) = .22, p<.05. Thus, the number of shots was included as a covariate
in all analyses concerning overall cry intensity at 6 months of age. Finally, there were no
significant differences among doctor’s offices with respect to any of the study variables.
Stability of Individual Differences in Infant Stress Responses. Descriptive information
concerning all infant and maternal variables is presented in Table 1. Zero-order correlations
Individual Differences 14
were conducted to assess the stability of overall cry intensity and overall cry duration These
analyses revealed that overall cry intensity was relatively stable, r (128) = .18, p < .05 while
overall cry duration was not stable across age (p < .49). General irritability showed marginal
stability across age, r (124) = .18, p = .05. After controlling for general irritability and number
of shots, the stability of overall cry intensity fell below statistical significance (p = .10).
Concurrent and Predictive Relations between Infant Stress Response Dimensions. To
assess the relations between overall cry intensity and overall cry duration, zero-order correlations
were conducted between these variables at both 2 and 6 months, controlling for general
irritability and number of shots. These variables were significantly concurrently related at both 2
months, r (124) = .25, p < .01, and 6 months, r (121) = .43, p < .001, but showed no significant
cross-variable longitudinal relations. Thus, infants who reacted more intensely to the inoculation
cried for longer periods than infants who responded with less intense crying.
Stability of Individual Difference in Specific Maternal Soothing Behaviors. Zero-order
correlations were conducted to assess the stability of specific maternal behaviors. These
analyses revealed that among the eight soothing behaviors measured, five were stable across age:
affection, r (126) = .33, p <.001, touching, r (128) = .31, p <.001, vocalizing, r (128) = .35, p <
.001, caretaking, r (128) = .19, p<.05, and feeding/pacifying, r (126) = .18, p < .05.
Correlation between Maternal Soothing Behaviors and Infant Reactivity. Prior to
examining the effectiveness of maternal regulatory behaviors, it is helpful to report the simple
concurrent correlations between each of the behaviors and the 2 and 6 month cry variables.
These data for a slightly larger sample were reported in a previous publication (reference omitted
for blind review) and data for the present, longitudinal sample are reproduced in Table 2. At 2
months, touching behavior was associated with decreasing cry intensity, whereas caretaking and
Individual Differences 15
distraction were associated with increasing cry duration. At 6 months, caretaking was associated
with increasing cry intensity, whereas affection, caretaking, and distraction were associated with
increasing cry duration.
Relation between Effective Maternal Soothing and Infant Stress Responses. The
correlation approach offers only limited information concerning associations between maternal
and infant behaviors. This approach makes it difficult to predict the direction of effects between
maternal and infant behaviors and therefore does not adequately capture the notion of effective
soothing. In line with the goal of the present investigation to examine the predictive association
between early effective maternal soothing and infant stress response four months later, we next
used contingency analyses to create an index of each mothers overall effectiveness. Because a
mother could have been effective in her use of a number of different behaviors, we created an
overall measure of effectiveness across all maternal behaviors for each mother-infant dyad. A
Yule’s Q value was calculated from 2 x 2 contingencies for each of the eight maternal behaviors
paired with lag-1 decreases in infant reactivity level. For each contingency, rows reflected the
presence or absence of a particular maternal behavior in a given interval and columns reflected
the presence or absence of a decrease in infant reactivity in each next interval (Lag 1). Yule’s Q
is a transformation of the odds ratio which reflects the odds that a given contingency will occur,
controlling for the base rate of behaviors. This value varies from -1 to +1 and serves as an index
of the strength of the contingency between two variables (Bakeman, 2000; Bakeman, McArthur,
& Quera, 1996; Van Egeren, Barratt, & Roach, 2001). Thus, in the context of our study, a
Yule’s Q value closest to +1 indicates that a behavior is strongly associated with decreases in
infants’ cry levels, zero indicates that the behavior has no effect on infants’ crying, and a value
closest to -1 indicates that the behavior is strongly associated with an absence of a decrease or an
Individual Differences 16
increase in infants’ crying. For each mother-infant dyad, a Yule’s Q contingency table was
created for each individual soothing behavior. Next, a mean Yule’s Q value for each soothing
behavior (across all mothers) was by summing the components of each dyad’s Yule’s Q.
At 2 months, the Yule’s Q values ranged from -1 to +1, and the mean value was .06 (SD
= .20). At 6 months, Yule’s Q values ranged from -.50 to +1, and the mean value was .01 (SD =
.18). The mean Yule’s Q value at 2 months was not significantly related to that at 6 months (p <
.88). The mean Yule’s Q at 2 months was not significantly related to any of the infant cry
variables at 2 months.
To test whether 2 month maternal soothing effectiveness was predictive of 6 month infant
cry duration, the 2 month Yule’s Q value was entered into a regression equation after accounting
for the variance due to 2 month overall cry duration. This test revealed that 2 month maternal
effectiveness was a significant predictor of 6 month overall cry duration (See Table 3). To test
the prediction of 6 month overall cry intensity by 2 month maternal soothing effectiveness, the 2
month Yule’s Q value was entered into a regression equation after accounting for the variance
due to 2 month overall cry intensity. This test revealed that 2 month Yule’s Q was not a
significant predictor of 6 month overall cry intensity (See Table 2). Thus, the index of mothers’
effectiveness at reducing infants crying at 2 months significantly predicted infants’ duration of
crying at 6 months but not the intensity of their response.
DISCUSSION
The current study is an extension of previous work on infant reactivity, maternal
soothing, and the effect of maternal soothing behaviors across early infancy. By observing
infants’ and mothers’ behaviors in response to an inoculation, our study examined individual
differences in infant pain reactivity, the maternal behaviors used to soothe infants in this context,
Individual Differences 17
and the longitudinal effect of early effective soothing on infants’ responses across time. Our
findings revealed that early maternal soothing behaviors predicted later infant reactivity
behaviors. Specifically, those infants whose mothers were more effective at soothing them at 2
months cried for a shorter duration 4 months later. Interestingly, early effective maternal
soothing did not predict later infant cry intensity. This finding not only supports the theory that
early regulatory experience with a caregiver influences emotional development over time (Kopp,
1989; Thompson, 1994), but also suggests that this effect may be specific to one parameter of
reactivity, duration, but not the parameter of intensity of reaction. One might speculate that at 6
months, both maternal and self-regulatory processes may have worked together to reduce the
duration of infants’ pain reaction. According to theories on the development of self-regulation,
associative learning may play a role in this process such that infants learn the rewarding nature of
reductions in distress, are thereby motivated to regulate their own emotions in the future
(Tompkins, 1962), and may later remember and call upon the appropriate modifiers of distress
(Kopp, 1989). Such a process would predict infants’ ability to quickly self-soothe or be soothed
by the mother, but not alter the intensity of their reaction to felt pain, suggesting the latter may be
a more stable temperamental characteristic.
Our findings concerning the individual stability in intensity of crying but not duration of
crying supports the view that cry intensity may reflect infant temperament. Specifically, we
found that overall intensity of infants’ crying in response to the inoculation was stable from 2 to
6 months. That is, infants maintained their relative rank along this dimension of reactivity over
time. This finding suggests that pain reactivity, like other types of negative reactivity, is an
enduring temperamental characteristic (Rothbart & Derryberry, 1981), and supports previous
Individual Differences 18
literature indicating stability in the intensity of infants’ and children’s pain response (e.g., Axia
& Bonichini, 1998; Worobey & Lewis, 1989; Izard et al., 1987; Shechter, et al., 1991).
However, infant cry duration was not found to be stable from 2 to 6 months. Previous
research with this age group has also found quieting in response to an inoculation to be unstable
(Lewis & Ramsay, 1995), and no relation between duration of crying to a heelstick at 2 days, and
to an inoculation at 2 months (Worobey & Lewis, 1989). This lack of stability in cry duration
may be due to the maturation process that takes place early in the first year of the infant’s life
whereby infants begin to engage in self-regulatory behaviors such as self-stimulation, selfsoothing, and redirecting of visual attention (Kopp, 1982; Rothbart, et al., 1992). Such selfregulatory behaviors may have worked in tandem with the soothing brought on by the mother to
quicken the infant’s recovery from inoculation. Thus, it may be that those infants with greater
self-regulatory maturation were more effective in regulating their distress to the inoculation at 6
months.
The lack of stability in duration of crying is in line with our finding that early effective
maternal regulation predicts infants’ duration of crying 4 months later. Together, these findings
suggest that early maternal intervention may be the source of instability in infants’ cry durations.
Furthermore, the lack of stability in duration of crying may have also reflected mothers’ abilities
to use a greater number of behaviors to soothe their older infants. Previous research suggests
that in the context of infant pain reactivity, mothers increase their use of vocalizing and
distraction behaviors as infants increase in age (Jahromi, Putnam, & Stifter, in press). These
behaviors require more work on the infants’ part and thus may reflect their burgeoning selfregulation. Distraction requires them to shift attention, and vocalization may activate memory of
the mother and her responsiveness. With maturation, infants become capable of responding to a
Individual Differences 19
greater number of soothing strategies and this may influence the duration of time it takes them to
be soothed. Our investigation of individual differences in the use of specific maternal behaviors
revealed that affection, touching, vocalizing, caretaking, and feeding/pacifying were stable
across time, indicating that mothers were consistent in their use of some, but not all, soothing
strategies. Interestingly, distraction was among those maternal strategies not found to be stable
across time. In line with the theory that infants’ attentional self-regulatory strategies emerge by
about 6 months (Rothbart et al., 1992), this finding may reflect the mothers’ recognition that
their infants may or may not respond to distraction as a means for soothing. In other words, with
increasing maturation and consolidation of individual differences in attention shifting ability,
mothers of infants who are able to be distracted used more of this strategy over time, whereas
mothers of infants who did not exhibit (as of yet) this skill used less (or the same amount of)
distraction over time. Thus, while our findings are relatively consistent with those of Lewis and
Ramsay (1999), who found that overall maternal soothing was stable between 2 and 4, and 4 and
6 months, the results of our study suggest that accounting for specific, rather than overall,
soothing behaviors helps to clarify whether mothers adjust their use of specific soothing
behaviors to match their infants’ developing skills. It should be noted, however, that our results
are specific to the inoculation setting, a context that is potent and consistent. Whether specific
maternal behaviors are stable across varying, less aversive, contexts is an important question for
future research.
The results of the present study point to a number of directions for future research on
maternal regulation of infant reactivity. As stated, future studies should explore the use and
effectiveness of specific caregiver behaviors in contexts other than the inoculation settings, such
as everyday settings and those involving less aversive sources of negativity. Also, future work
Individual Differences 20
should explore the antecedents of individual differences in maternal soothing behaviors.
Thompson (1997) proposes that a variety of diverse factors, such as parental schemas and
situational stressors, may influence parents’ sensitivity and responsiveness to their infants.
These factors may also play a role in shaping parents’ soothing repertoires and research
concerning this issue may explain indirect effects on infants’ external soothing environment.
Finally, in line with our finding that infant self-regulation may be predicted by early effective
maternal soothing, and the fact that previous research has found individual variability in infants’
use of self-regulatory strategies within the first year of life (e.g., Braungart & Stifter, 1996; Fish,
Stifter, & Belsky, 1991; Riese, 1987), an important direction for future research is to examine
whether those infants who experience early effective soothing display a greater ability to selfsoothe as they develop.
In sum, the present study found that infants of mothers who were effective at soothing
their distress at 2 months showed a shorter duration of crying 4 months later. This finding may
explain the lack of stability in the duration of infant crying that was found in previous research.
The intensity of infant’s stress responses and many of the specific maternal behaviors studied,
however, showed stability over time. This study extends the previous research on the
longitudinal effect of maternal soothing behaviors, and supports much of the research on the
effect of other maternal behaviors such as sensitivity and responsiveness.
Individual Differences 21
ACKNOWLEDGMENTS
The study was supported by a grant from the National Institutes of Mental Health
(MH50843) awarded to the second author. We would like to thank all the consultants, students,
and staff who worked on this project. Special thanks go to the families who participated in the
Emotional Beginnings Project.
Individual Differences 22
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Individual Differences 28
Table 1
Means, Standard Deviations, and Ranges for Infant and Maternal Variables
2 Month
M
SD
6 Month
Range
M
SD
Range
Infant Variables
Overall Cry Intensitya
1.63
.45
.66 – 2.92
1.32
.50
.17 – 2.90
Overall Cry Durationb
27.98
12.47
7.00 – 48.00
22.27
12.47
5.00 – 48.00
Maternal Variables
Affectionc
.27
.25
.00 – .93
.18
.17
.00 – .75
Touching
.39
.25
.00 – 1.00
.32
.23
.00 – .92
Holding/Rocking
.82
.21
.00 – 1.00
.81
.24
.00 – 1.00
Vocalizing
.66
.22
.09 – 1.00
.71
.24
.00 – 1.00
Caretaking
.07
.13
.00 – .63
.07
.16
.00 – .85
Distracting
.01
.04
.00 – .42
.07
.12
.00 – .55
Presenting face
.34
.27
.00 – 1.00
.39
.29
.00 – 1.00
Feeding/Pacifying
.19
.28
.00 – 1.00
.17
.28
.00 – 1.00
a
b
Note: Overall cry intensity was measured on a scale ranging from 0 to 3. Overall cry duration reflects number of 5-second intervals.
c
Maternal behaviors reflect the proportion of time that the mother engaged in a specific behavior.
Individual Differences 29
Table 2
Correlations between Maternal Behaviors and Cry Variables at 2 and 6 Months
2 Montha
Maternal Behavior
6 Monthb
Cry Intensity
Cry Duration
Cry Intensity
Cry Duration
Affectionc
.04
.01
.14
.19*
Touching
-.21*
.01
-.04
-.08
Holding/Rocking
-.08
-.07
.02
.11
Vocalizing
.05
.09
.15
.10
Caretaking
.11
.20*
.21*
.35**
Distracting
.16
.26**
.04
.21*
Presenting face
.05
.09
.02
.00
Feeding/Pacifying
.05
.07
.00
-.04
Note. an = 128; bn= 127. * p < .05; **p <.01; Correlations are Spearman’s correlations; cValues represent the mean proportion of
time spent engaging in that type of maternal behavior.
Individual Differences 30
Table 3
Regression Analyses for Prediction of 6 Month Infant Reactivity Variables by 2 Month Infant Reactivity and 2 Month Effectiveness of
Maternal Soothing (N = 127)
β
Standard Error
R2
F
.02
.09
.04
2.56†
-.20*
5.45
1 2 month overall cry intensity
.18*
.10
.05
3.12*
2 2 month effective maternal soothing
-.13
.21
Variables in the model
6 month overall cry duration
1 2 month overall cry duration
2 2 month effective maternal soothing
6 month overall cry intensity
Note. †p < .06, *p < .05.